J.G.M. Hans Thewissen
Ingalls-Brown Professor of Anatomy
Ph.D., University of Michigan
Mammalian Anatomy, Development, and Evolution
My research interests center around the evolutionary patterns associated with major morphological shifts in mammalian evolution. These patterns are the best model systems for the study of evolutionary processes because they document most directly the interaction of phylogeny, functional morphology, ontogeny, and environment. To gain as full an understanding of evolutionary shifts as possible, my research program uses data from a variety of subdisciplines, including paleontology, anatomy and embryology. Overall, my research is question-driven, I use any method that can help in unraveling relevant problems, and take advantage of emerging techniques to explore questions that were previously unanswerable.
Specific morphological shifts that I have been interested in are the origin of flight in bats and its relevance to the higher phylogeny of primates and the emergence of aquatic adaptations in whales (cetaceans). The latter is a major ongoing project, focusing on the study of those cetaceans that document the land to water transition and its developmental underpinnings as well as the adaptations of modern cetaceans. Fossil data provide direct evidence of the evolutionary transition while the analyses of modern species offer a functional and genetic framework for interpreting the fossil data.
Of special interest are the emerging adaptations of the organ systems involved with hearing, balance, locomotion, and osmoregulation, as these systems underwent dramatic change. The ultimate goal of this work is to provide a detailed account of the evolving adaptations in early whales, and to use this account to identify the constraints on cetacean evolution.
This project is large and growing and involves paleontological and sedimentological fieldwork in India, study of the embryology and development biology, the functional morphology of locomotor organs, geochemistry of dental tissues, the biophysical properties of modern dolphin earbones and phylogenetic analysis.